JP2851843B2 - Switching type power supply for video display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial applications>   The present invention relates to a switching power supply for a video display device.
The present invention relates to a switching power supply device including a supply source. <Background of the Invention>   For example, flyback converter type switching type
In the power supply, the rectified line supply voltage is
Is supplied to the primary winding. Driven by control circuit
A chopper switch regulates the secondary winding voltage. Power transformation
The transformer was coupled to the power supply and the secondary winding of the power transformer
An electrically insulating barrier between the electrically isolated load circuit and
May act. To maintain electrical insulation
The voltage feedback to the control circuit is electrically performed from the secondary winding.
This is done via an insulated feedback winding.   Television receiving with switching power supply
When the device or video display is activated,
Generated by one of the electrically isolated secondary windings
Rectified, the B + deflection voltage for the horizontal deflection circuit becomes
Generated. For example another electrically insulated secondary
The voltage generated by the winding is rectified to produce a stereo sound.
Large power consumption such as voice circuit and load size changes
A DC supply voltage for another load is generated. Feedback winding
Leakage inductance exists between the coil and the secondary winding
Because the feedback winding voltage is heavy due to, for example, an audio circuit
Does not accurately represent the output voltage of the secondary winding when changes
Sometimes. If one of the load circuits is a horizontal deflection circuit
If the output voltage adjustment is not good, the raster width will be outstanding
May change.   That is, the switching type power supply with the conventional configuration
Is connected to a load having a large load fluctuation.
The output voltage of the secondary winding is not accurately reflected in the feedback winding voltage
Therefore, the output voltage cannot be adjusted accurately.
There is a title. <Summary of the Invention>   The purpose of the present invention is to solve the disadvantageous effects of large power load fluctuations.
Switch with feedback voltage configuration that can eliminate
The present invention is to provide a switching power supply. Output switch
Switches the first winding, which is the primary winding of the power transformer, to energy
It binds to the giant source. The deflection circuit of the video display device
A second load, which is a secondary winding of the generator, is connected to a first load circuit.
To receive energy from the energy source and
Generate data. The second load circuit is a secondary winding of the power transformer.
Coupled to a third winding that is a wire and receives energy therefrom.
Take away. A first feedback winding is positioned near the second winding.
And a first feedback representing a change in load on the power transformer.
Generates voltage. The second feedback winding is
A power transformer located farther than the first feedback winding
Generating a second feedback voltage representing a change in load applied to the
You. A control circuit is coupled to the first and second feedback windings
Has an input circuit and an output circuit coupled to the output switch
And switches the output switch according to the first and second feedback voltages.
Transfer of energy between the energy source and the deflection circuit
To adjust. Therefore, the power is supplied from the second winding to the deflection circuit.
Energy is precisely adjusted, thereby increasing the size of the raster.
Is stabilized. <Detailed description of the embodiment>   In FIG. 1, a switching power supply 20 is
Various load circuits for vision receivers or video display devices
To supply power. Switching power supply source 20
And the AC line power supply voltage source 21
Coupled between terminals 22 and 23, output terminal 24 and current
Unadjusted DC supply voltage Vin between return terminal 25
Is done. Filter capacitor C7 connects output terminal 24 with current
It is coupled to the return terminal 25. Current return
Terminal 25 is electrically insulated from AC line power supply voltage source 21.
The contacts shown as "hot" ground points in FIG.
Acts as ground terminal 60.   Unregulated DC supply voltage Vin is a switching power transformer
It is supplied to the primary winding P of the device T1. Chopper switch
Transistor Q1 is coupled to primary winding P and switched
It is generated by the mode control circuit 29 and the
Switching voltage V supplied to the input gate electrode_GBy
Driven. The sampling resistor R5 for overcurrent protection is
Primary winding P and chopper switch transistor Q1
The flowing current is sampled. Sampling resistor R5
The voltage generated between both ends is switched to the switching mode via the signal line 36.
Supplied to the control circuit 29 and switched on in overload operation.
Voltage V_GStop the occurrence of   Switching of chopper switch transistor Q1
As a result, an AC voltage is generated across the primary winding P, and
This generates an AC voltage across the secondary windings S1, S2 and S3.
Live. Depending on the relative winding polarity of the primary and secondary windings,
Operation in flyback converter mode.
You. The switching mode control circuit 29 performs, for example, a pulse width adjustment operation.
Operation, or constant on-time operation at a variable frequency, or
An operation combining these two operations is performed.   In this example, the AC generated at both ends of the secondary winding S1 for the audio circuit
The voltage is applied during the flyback period of each switching period.
Half-wave rectified by the diode D1 and by the capacitor C1.
To produce a DC supply voltage V1
Electric power is supplied to the teleo audio circuit 30. Secondary winding S2
The AC voltage developed across the
Rectified by diode D2 and filtered by capacitor C2
This generates a DC supply voltage V2, for example,
Other load circuits 31, such as a mininance-chrominance processing stage
Is supplied with power.   The AC voltage generated across the secondary winding S3 is a diode
Rectified by D3, filtered by capacitor C3,
This generates the DC supply voltage B + and the horizontal deflection circuit
Supplied to 40. The horizontal deflection circuit 40 has a horizontal deflection winding L
_HThe horizontal deflection voltage whose amplitude is a function of the amplitude of the DC voltage B +
Generate a flow. The horizontal deflection circuit 40 is a retrace pallet.
This retrace pulse voltage is applied to the horizontal
The primary winding W1 of the ryback transformer T2 is supplied to the
The retrace pulse voltage on the secondary windings W2, W3 and W4
Generated.   The voltage generated across the secondary winding W2 is a diode D6
Rectified and filtered by capacitor C6.
As a result, a DC supply voltage V4 is generated and supplied to the vertical deflection circuit 32.
Supplied. Generated between both ends of the secondary winding W4 which is a high voltage winding
The generated voltage is supplied to the high-voltage circuit 50, which
When the ulta acceleration potential is generated at the
It is supplied to a picture tube (not shown) of the receiver.   Retrace pulse voltage generated between both ends of the secondary winding W3
Pressure, e.g. video blanking and high voltage interruptions
The control information and the synchronization information for stopping are obtained. For example,
Retrace pulse voltage generated by secondary winding W3
Is supplied to the high-voltage stop circuit 33,
Signal line in response to excessive retrace pulse amplitude
At 35, a stop signal SD is generated. This stop signal is in switching mode
The chopper, switch, and transistor
The operation of the star Q1 is stopped in a stopped state.   Normal on-off control under remote control
And the output of the remote receiver 28 is connected to the switch transistor Q2.
Supplied, this switch transistor Q2 is turned on and off
・ Controls coil energization of relay RL. Television receiver
The machine from standby mode operation to normal run mode operation.
Relay coil to switch
Controlled by the remote control signal receiver 28 via the Q2
The mechanical switch part of the relay RL is a hot ground terminal
60, whereby the signal line 34 is grounded. signal
When the line 34 is grounded, the switching mode control circuit 29
Is energized to begin normal operation and the chopper switch
・ Switching voltage V supplied to transistor Q1_GDepart
Live.   The standby power supply 27 is a remote control signal receiver 28 and
Supplied to the coil of the on-off relay RL
A Supply voltage V_SBOccurs. This standby supply voltage V_SB
Is supplied with standby power by down converter T3
It is derived from the AC line supply voltage supplied to source 27.   Avoid electrical shock from AC line power supply voltage source 21
Most of the circuitry of the television receiver is
1 electrically shown as a "cold" ground point in FIG.
Connect with reference to the return terminal 70, which is an insulated ground point.
It is grounded. Hot grounded end that is not electrically isolated
Components and circuits that are grounded with respect to
Relatively small. As shown in FIG.
Signal or power is supplied across the insulation barrier 80
Relatively few places are done.   The electrical insulation barrier is the primary winding of the standby transformer T3
Between the coil of the on-off relay RL and the
Between the mechanical switch and the input of the high voltage stop circuit 33
It is provided between the power unit and the output unit. High voltage stop circuit
The insulation barrier for 33 is provided using, for example, an optical coupling element.
Can be   Another electrical isolation barrier is the switching power transformer
It is formed by T1. Primary winding P and chopper
The switch transistor Q1 is supplied from the AC line power supply voltage source 21.
The secondary windings S1, S2 and
And S3 are electrically isolated from the AC line power supply voltage source 21.
You. The advantage of this is that the switching mode control circuit 29
Is not insulated from mains voltage line 21 and
Switching voltage V_GThe chopper switch transistor
Q1 can be supplied in the form of DC coupling. In this configuration
Therefore, in the drive section of the chopper switch or
It is necessary to provide another electrical isolation point at the flow overload sensing point.
No need.   The switching mode control circuit 29 uses the hot ground terminal 60 as a reference.
Output voltage is regulated while the
Ground point where the supply voltages B +, V1 and V2 are electrically insulated
Is grounded with reference to the return terminal 70
Therefore, output voltage feedback information should not be supplied across insulation barrier 80.
I have to. The signal representing the output voltage is
Switching type power transformer to supply to hot side
The feedback winding FB1 of T1 is grounded with respect to the hot ground point.
ing. The voltage generated across the feedback winding FB1 is
Diode D4 during the flyback period of the switching period
Rectified, filtered by capacitor C4,
Feedback voltage V_FB1Is generated.   This DC feedback voltage V_FB1Is the movable end of potentiometer R1
Through the movable terminal and the hot ground terminal 60
Resistor R2, potentiometer R3 and resistor R4 coupled between
Of the potentiometer R3 of the voltage divider
Supplied to the error input terminal E of the switching mode control circuit 29.
It is. The switching mode control circuit 29 outputs the feedback voltage V_FB1By
In accordance with the change in the secondary winding output voltage which is partially represented,
Switching voltage V_GTo change.   Feedback voltage V_FB1Is also a standard television receiver.
DC mode to the switching mode control circuit 29 during
Supply voltage V_CCAct as This DC supply voltage V_CCIs
During the standby mode, the voltage drops from the unregulated input voltage Vin.
Supplied through anti-R7 and diode D7. With drop resistance R7
Zener diode connected to the connection point with diode 7
When Z1 is in standby mode, the DC supply voltage V_CCTo
Stabilize. Diode D7 operates in normal run mode
Medium, feedback voltage V_FB1Reverse bias.   Many television receivers have a provision for a horizontal deflection circuit.
It is necessary to strictly adjust the supply voltage B +. Supply voltage B
Inconvenient change in raster size even if + change is small
Tends to occur.   The supply voltage B + is not directly sensed, for example the winding of FIG.
A field sensed by an isolated feedback winding such as FB1
In this case, it may be difficult to adjust the supply voltage B + well.
You. This adjustment is difficult because the feedback winding is a secondary winding
Voltage cannot be sensed accurately
You. As an example, consider the power supply of FIG. S
The switching power supply 20 provides three secondary power supplies.
Pressure, that is, the deflection supply voltage B +, and each channel has 5 watts.
Audio power supply for supplying power to the stereo audio circuit 30
The voltage V1 and the load circuit 31 are collectively shown in FIG.
Power to the various other television receiver loads shown
The supply voltage V2 to be supplied is obtained.   Dynamic load characteristics seen in these three supply voltages
Sex is completely different. The supply voltage B + is applied to the horizontal deflection circuit 40.
Power supply, and flyback metamorphosis
Power to the high-voltage circuit 50 and the vertical deflection circuit 32 via the detector T2.
Supply. When a remarkable change occurs in the supply voltage B +,
Raster dimensions vary significantly both in width and height. voice
The dynamic load characteristics of the supply voltage V1
Changes greatly depending on the content of the
You. Supply voltage V2 mainly powers low-level signal circuits
Therefore, the load is relatively constant. This supply voltage
Even if V2 changes significantly, a linear regulator will be connected in series with that load.
Can be provided so that the change is acceptable
You.   The volume control of the stereo audio circuit 30 is set to the high volume position.
Supply voltage B + is a function of the content of the audio program
May change. This reduces the raster dimensions
The disadvantage of changing as a function of the content of the audio program
May produce unpredictable results.   Change in supply voltage B + induced by audio load
The factor to give is the secondary winding S of the switching type power transformer T1.
1, the existence and existence of leakage inductance between S2 and S3
Is the distribution of FIG. 2A shows a single unit shown as winding FB.
Of the power transformer T 'when only the feedback winding of
1 schematically shows the structure. With only a single feedback winding
Accurate supply without noticeable modulation by voice load
It is difficult to adjust the voltage B +. FIG. 2B shows the first
This can be used as switching power transformer T1 in the figure
Fig. 3 shows the structure of a power transformer according to one aspect of the invention;
In this structure, two feedback windings FB1 and FB2 will be explained later.
It is provided for the purpose of doing.   The power transformers T1 'and T1 have the same configuration except for the period winding.
It is made. FIG. 2A and FIG. 2B show only a part.
There are no windings, but all windings are
Plastic bobbi attached to the center leg of the light core
It is a layer wound on top. The cross section of the center leg
In the example of about 1.9cm^Two(0.29 square inches). Each layer
The winding turn of this example is 30 gauge (0.2546m
m) consisting of 7 strands of enamelled copper wire
The height of each layer is 0.76 mm (30 mil). Each layer
Has a winding width of about 18 mm (0.7 inch).   The primary winding P has two layers P_AAnd P_BEach layer consists of 12
Consists of Two secondary windings S3 for supply voltage B +
Layer S3_AAnd S3_BAnd each layer consists of 14 turns. sound
One secondary winding S1 for voice supply voltage V1 consisting of 6 turns
And the secondary winding S2 consists of 4 turns.
It consists of three layers.   Secondary windings S1 and S2 occupy the same layer and are located side by side
The center of the winding width of the secondary winding S1 is at the position CLS1,
The center of the winding width of the secondary winding S2 is at the position CLS2. Secondary winding
The layer consisting of S1 and S2 is the layer S3 of the secondary winding S3_AAnd S3_BBetween
Are located in Layer S3_AIs the layer P of the primary winding P_ARolled up
On the other hand, the layer P of the primary winding P_BIs the secondary winding
S3 layer S3_BIt is wound up and formed. in this way,
The three layers of the secondary winding are located between the two layers of the primary winding.
Have been.   Confirm the electrical shock from the AC line power supply voltage source 21 shown in FIG.
Suitable thickness, for example, 0.15 mm
(6 mil) Mylar insulation tape next to each layer of primary winding
It is provided between each layer of the secondary winding that is in contact with it. Thickness
Thinner, for example, 0.05 mm (2 mil) Mylar insulation tape
Are provided between adjacent layers of the secondary winding.   As mentioned above, the supply voltage B + needs to be precisely adjusted.
Yes, the supply voltage with the largest load change is the audio supply
The voltage is V1. Now, for convenience of explanation, the flybar shown in FIG.
Power transformer T1 'is the power isolation transformer of Fig. 1.
It is shown in Fig. 2A as a three-turn winding FB
Mode control using only one feedback winding
Error voltage V for circuit 29_EIs generated.   As a first alternative, precise adjustment of the supply voltage B +
For example, secondary winding S3 for supply voltage B + and secondary winding for audio
In an ideal situation where the magnetic coupling with S1 is very sparse
Is achieved. Magnetic coupling between primary windings S3 and S1
Is sparse, large load changes on the secondary winding S1
Very little effect on the voltage generated by the secondary winding S3
small.   As a second alternative, precise adjustment of the supply voltage B +
Is, for example, the secondary winding S3 and the feedback winding FB of the power transformer T1 '.
In an ideal situation where the magnetic coupling between
Is done. What is the voltage change that occurs in the secondary winding S3
But the feedback winding FB magnetically tightly coupled to this
Accurately sensed.   As a third alternative, precise adjustment of the supply voltage B +
Is, for example, a magnetic coupling between the feedback winding FB and the secondary winding S3.
And the magnetic coupling between the feedback winding FB and the secondary winding S1 is maintained at a critical value.
Achieved in the ideal situation held. If return winding
The magnetic coupling between the wire FB and the secondary winding S1 is equal to the feedback winding FB and the secondary winding.
If it is too dense compared to the magnetic coupling with line S3, the switching mode
Mode control circuit 29 responds excessively to changes in voice load.
You. Oversupplied supply voltage B + due to large dynamic audio load
This causes the supply voltage B + to be heavy
Increases under load conditions. With this increased supply voltage B +
Therefore, the raster size increases. If the feedback winding FB and the secondary winding
The magnetic coupling between the wire S1 and the feedback winding FB and the secondary winding S3
Is too sparse compared to dynamic coupling, and the feedback winding FB and secondary
If the magnetic coupling with winding S3 is not perfect, the opposite result
This results in reduced raster dimensions.   Magnetic coupling between feedback winding FB and secondary winding S1 and feedback winding
The magnetic coupling between the FB and the secondary winding S3 is set to a critical value.
Therefore, the feedback voltage generated by the feedback winding FB is
It is relatively insensitive to load changes, which
There is no change in raster dimensions due to load.   The overall transformer winding structure is mainly based on economic conditions and manufacturing
Is determined by taking into account the
The two alternative configurations are, in practice, a power isolation transformer.
Relatively inconvenient structural and design choices to obtain
Have a problem.   Although the third alternative configuration is feasible, this configuration
Then, the magnetic coupling between the feedback winding FB and the secondary winding S3 and the feedback winding
There is a critical value for the magnetic coupling between the line FB and the secondary winding S1. this
It would be difficult to mass produce such transformers. plus
The horizontal arrangement of the feedback winding FB on the tick bobbin
Any deviation, supply voltage B + is ± 1V or more
May change. Inconvenient changes in raster dimensions
What happens when the supply voltage B + changes more than ± 0.4V
There is. In addition, the separation between each turn of the feedback winding FB is accurate.
May be strict due to the voltage adjustment.   According to a feature of the invention, the two feedback windings of FIG.
A transformer winding configuration provided with FB1 and FB2 is used.
The voltage generated between the two feedback windings FB1 and FB2
Is rectified and filtered as shown in FIG.
Pressure V_FB1And V_FB2Is generated. Generated by feedback winding FB2
The rectification of the generated voltage is a
This is done by diode D5 during feedback
This is performed by the capacitor C5. Feedback voltage V_FB1And V_FB2When
Is relatively added by potentiometer R1, which
Is added to the movable terminal of potentiometer R1.
Return voltage V_FIs connected to resistor R2, potentiometer R3 and resistor R4
Therefore, the voltage is divided and an error is applied to the movable terminal of potentiometer R3.
ー Voltage V_EIs generated, whereby the switching mode control circuit
29 operations are controlled.   FIG. 2B shows a bobbin of the switching type power transformer T1.
Above shows the arrangement of the three-turn feedback windings FB1 and FB2.
Have been. According to one aspect of the invention, a feedback winding FB
1 is a position that is highly magnetically coupled to the secondary winding S1 for audio.
On the bobbin in a horizontal or transverse direction
You. As shown in FIG. 2B, the winding width of the feedback winding FB1
Center CLF1 is located above the center CLS1 of the winding width of the secondary winding S1.
Is placed. Furthermore, the end turn of the feedback winding FB1 is
It is arranged laterally in the end turns of the secondary winding S1.   According to another feature of the invention, a second feedback winding is provided.
FB2 is located on the bobbin of switching power transformer T1.
The magnetic coupling between the feedback winding FB2 and the secondary winding S1 is
Be less sparse than the magnetic coupling between B1 and secondary winding S1
Are located. When implementing this feature, the feedback winding FB2
The center CLF2 of the winding width of the secondary winding S2 is the center CLS2 of the winding width of the secondary winding S2.
Placed on top. The end turn of the feedback winding FB2 is a secondary winding
It is located laterally within the end turn of line S2.   The feedback windings FB1 and FB2 are arranged as described above.
Therefore, the advantage that the tolerance of the transformer structure is increased
There is.   Magnetic coupling between secondary winding S1 and two feedback windings FB1 and FB2
Are different, the two feedback windings are
Respond differently to The feedback winding FB1 is the secondary winding S2
Magnetically more tightly coupled to secondary winding S1 than to
When a heavy voice load occurs, the magnetic coupling becomes less
Feedback voltage V obtained from the feedback winding FB2_FB2More return
Voltage V_FB1Tend to decrease. These two feedback currents
Pressure V_FB1And FB_FB2Is proportionally added by potentiometer R1
The feedback voltage V_FB1Feedback voltage V_FB2Relative to
Effect is controlled by adjusting potentiometer R1.
Wear.   The movable terminal of potentiometer R1 in FIG.
To the feedback voltage V_FB2Is the feedback voltage V_FBy
It takes heavy. Conversely, the movable terminal of potentiometer R1 is downward
To the feedback voltage V_FB1Is heavier and the feedback voltage
V_FIt takes Therefore, simply adjust potentiometer R1.
The effect of the voice load on the secondary winding S1
Therefore, the tendency that the supply voltage B + is modulated becomes zero.
Adjusted. Feedback voltage V_FThe effect on the
Pressure V_FB1And V_FB2Can easily be harmonized with
This harmonization results in strict winding tolerances required for transformer structures.
The difference is mitigated.   The table below shows the case where there is no audio load and the case where the audio load is maximum.
Moved the movable terminal of potentiometer R1 in case
Supply voltage B + for position, feedback voltage V_FB1And V_FB2And la
The measured value of the change in the star width is shown. This measurement is
Switching mode power supply similar to switching power supply 20
The source has a 110-degree, 26-inch, in-line picture tube
This was done using a color television receiver. This
To simulate maximum voice load when measuring
Connect a 47 ohm resistor across the audio supply voltage V1
did. Also, to simulate 0 voice load,
Was removed from the audio supply voltage V1. In the table below
Indicates that the feedback windings FB1 and FB2
The relative influence on the adjustment of the pressure B + is shown.  The movable terminal of potentiometer R1 is a switching type
In the negative feedback regulation loop of force transformer 20. Switching mode system
The control circuit 29 has a feedback voltage V_FIs kept substantially constant
Supplied to the chopper switch transistor Q1
Switching voltage V_GTo change.   The movable terminal of potentiometer R1 is moved upward and
Between the movable terminal and terminal E1
Of the movable terminal and the terminal E2
The resistance value between them becomes maximum. Therefore, the feedback voltage V_FIs magnetic
Voltage V obtained from feedback winding FB2 with poor coupling_FB2of
Magnetic coupling rather than changes caused by audio loading
Feedback voltage V obtained from tightly coupled feedback winding FB1_FB1Voice of
Be more responsive to changes caused by load.   In this case, the switching mode control circuit 29 outputs the feedback voltage V_FB1of
The secondary winding output voltage is adjusted according to the change. upper
As shown in the table, the movable terminal of potentiometer R1 is
When moved near the terminal E1, the feedback voltage V_FB1Is the switching mode
If there is no audio load as adjusted by the control circuit 29
Thus, the voice load is kept relatively constant until the maximum.   However, in such a situation, the supply voltage B + is over-adjusted.
130.0 volt level for no audio load
131.2 volt level for maximum audio load from
Increase to the bell. As a result, when the load is
The disadvantage is that the width of the tape expands by about 1.27 cm (about 0.5 inch)
Occurs.   Over-adjustment of the supply voltage B + is performed by the feedback winding FB1 and the secondary winding S1.
Due to tighter magnetic coupling with sound
When the voice load is at its maximum, during the chopper flyback period
The amount of decrease in the voltage across the feedback winding FB1 in the secondary winding
It is larger than the amount of decrease in the voltage between both ends of the line S3. Feedback winding
Switching mode control that responds directly to a decrease in voltage across FB1
The control circuit 29 is a switch for the chopper switch transistor Q1.
Adjust the switching between the two ends of the feedback winding FB1.
Is restored to the previous level. This switch
Switching control of the chopper switch transistor Q1
As a result, the amplitude of the voltage across the secondary winding S3
Greater than the amplitude required to maintain the level of pressure B + constant
And this supply voltage B + is
As the raster width increases, the raster width increases.   The movable terminal of potentiometer R1 is moved downward and
When it comes to the lower position, the resistance between this movable terminal and terminal E2
Value is minimized and the resistance between this movable terminal and terminal E1
Is maximized, and again in a similar situation
You. Feedback voltage V_FIs the feedback voltage V_FB1Than the feedback voltage V_FB2To
Therefore, it is greatly affected.   As shown in the table above, movable potentiometer R1
When the terminal is moved near terminal E2, the switching mode control circuit
Path 29 is the feedback voltage V_FB2From no voice load to voice negative
Voice by keeping the load relatively constant until the maximum load
Respond to changes in load. As a result, adjustment of the supply voltage B +
Becomes insufficient and the supply voltage B + becomes
It decreases from the level when there is no voice load. By this
The raster width is reduced by about 1.27cm (0.5 inch)
Inconvenience occurs.   Compare magnetic coupling of feedback winding FB2 to secondary winding S1
2+ for B + power supply due to increased voice load
Even if the amplitude of the voltage generated across the
The return winding FB2 is not significantly affected by the return winding FB2.
The voltage across line BF2 does not decrease sufficiently. Obedience
Therefore, the switching mode control circuit 29 outputs the supply voltage B +
Constant supply voltage B + is maintained even when the load level increases
Can not be restored to the level necessary for
No.   According to one aspect of the invention, the feedback voltage V_FGenerate
The relative action of feedback windings FB1 and FB2 for
The change in pressure B + is the case where there is no voice load and the case where the voice load is maximum.
It can be adjusted to be relatively small between cases. Pote
Connect the movable terminal of potentiometer R1 to this potentiometer R1.
By adjusting to the intermediate position at the intermediate terminal I,
Feedback voltage V_FB1And V_FB2Is proportionally added at this movable terminal.
Of the feedback winding FB1 during the period when the audio load increases.
Of the compensation of the degree and the effect of the insufficient compensation of the feedback winding FB2
Is offset   As shown in the table above, movable potentiometer R1
When the terminal is located at the intermediate terminal I, the supply voltage B +
Relatively one-way from no load to maximum voice load
This means that the raster width will be
No significant change occurs between states.   Two feedback voltages V_FB1And V_FB2The equilibrium effect with
You can also see from the values shown in the last line. These two feedback voltages
V_FB1And V_FB2Switching mode system
The control circuit 29 has a feedback voltage V_FTo keep the audio relatively constant
Feedback voltage V due to increased load_FB1Against changes in
Responding insufficiently while the voice load increased.
Feedback voltage V_FB2Responds excessively to changes in
The net effect is that the two feedback voltages V_FB1And V_FB2And to
Response is relatively constant with supply voltage B + and raster width
Is to balance (balance).   Connect the movable terminal of potentiometer R1 to the intermediate equilibrium point in Fig. 1.
The adjustment processing arranged at the terminal I is as follows. First, the sound
The supply voltage B + when there is no voice load is measured. For partial pressure
Connect the movable terminal of potentiometer R3 to a specific supply voltage B +
To obtain an error voltage that gives
You. Next, the maximum level of audio load is applied to the secondary winding S1
So, for example, the equivalent resistor is
Place between both ends. Furthermore, the supply voltage B + is measured again.
The movable terminal of potentiometer R1 is connected to supply voltage B +.
Adjust to a position that restores to a constant level. in this way
Adjustable potentiometer R1 movable terminal has intermediate balance
It is located at point terminal I.   Feedback voltage V_FB1And V_FB2Is a switching power transformer
T1 structural tolerance and forward direction between diodes D4 and D5
Normally when there is no audio load due to the difference in voltage drop
Not equal. As a result, the potentiometer R1
Adjustment of the moving terminal is performed by the initial setting of the moving terminal of potentiometer R3.
Affect settings. Therefore, usually a potentiometer
Repeat the adjustment process several times until R1 and R3 are set properly.
Need to be returned.   According to one aspect of the invention, the load resistance R_LFigure 1
Is disposed between both ends of the filter capacitor C5. This negative
Load resistance R_LIs connected to the switching mode control circuit 29 by the feedback winding FB1.
Voltage V_CCSubstantially the same as the load applied by the supply
An amount of load is applied to the feedback winding FB2. These two returns
The load applied to windings FB1 and FB2 must be equivalent, that is, matched.
Because the feedback voltage V, which is a rectified DC voltage_FB1When
V_FB2Becomes almost equal at this time, and the potentiometer R1
Because the change in supply voltage B + decreases with the adjustment of
is there.   FIG. 3 shows the process of adjusting the supply voltage B + described above.
Effective effects are shown. In FIG.
The anti-43 is the stereo when the voice load in FIG.
O Equivalent to the load resistance of the audio circuit 30 and is controlled by the transistor Q3.
And is applied across the supply voltage V1. This
The switching frequency of transistor Q3 is
5Hz square wave generator 4 coupled to the base of transistor Q3
Controlled by 12. Depending on the load by switching the load resistance 43
Supply to measure the change in supply voltage B +
The voltage B + is AC-coupled through the capacitor 44 and
Hz low-pass filter 45, filtered by AC voltmeter 46
Supplied.   Using the circuit of FIG. 3, adjust the potentiometers R1 and R3.
Adjustment of B + deflection voltage by impedance circuit including
It is as follows. 5Hz square wave generator 41 is deactivated and audio negative
Adjust the potentiometer R3 when there is no load to
The supply voltage B + is obtained. Activate the 5Hz square wave generator 41 to
Supply voltage V1 of load resistor 43 at 5 Hz frequency of square wave generator 41
Are alternately connected and disconnected. This load resistance
By switching 43, the load of switching power transformer T1
In the case where there is no load on the secondary winding S1 for audio and when the load is
There is a 5 Hz change from the large case.   The movable terminal of potentiometer R1 is the intermediate equilibrium point in Fig. 1.
Assuming that it is not located at terminal I, switching of load resistance 43
This causes a 5 Hz modulation in the level of the supply voltage B +.
The amplitude of this B + modulation is measured by AC voltmeter 46.
Next, the movable terminal of potentiometer R1 is
Adjusted to indicate zero volts. AC voltmeter 46 is zero
The movable terminal of potentiometer R1 is properly
The terminal I is set to the intermediate equilibrium point terminal,
Even if there is a load change in the winding S1, the level of the supply voltage B + changes.
The modulation of the shared voltage B + to substantially zero
You can do it.   Reason for choosing 5Hz frequency to switch load resistance 43
This 5Hz frequency causes ripple in supply voltage B +
Is significantly different from the vertical deflection frequency
You. The supply voltage B is determined by the third-order 10 Hz low-pass filter 45.
+ Vertical frequency ripple component is measured by AC voltmeter 46
Is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an embodiment of a switching type power supply device for a video display device of the present invention, and FIG. 2A is a diagram showing a case where only a single feedback winding is provided. FIG. 2B is a diagram schematically showing the structure of a power transformer that can be used in the switching type power supply device of FIG. 2, FIG. 2B is a diagram schematically showing the structure of the power transformer of FIG. FIG. 3 is a diagram showing a set-up circuit used to appropriately adjust the setting of the potentiometer of the switching power supply of FIG. 26 ... energy source, 29 ... control circuit, 40 ... deflection circuit,
53: secondary winding of power transformer T1, T1 ... power transformer, P
…… Primary winding of power transformer T1, Q1 …… Output switching means, FB
1 ... first feedback winding of power transformer T1, FB2 ... second feedback winding of power transformer T1.

Claims (1)

(57) [Claims] An energy source; a power transformer; output switching means for coupling a first winding of the power transformer to the energy source; and an energy source coupled as a load circuit to a second winding of the power transformer. A deflection circuit of a video display device for receiving energy from the first and generating a raster; a second load circuit coupled to and receiving energy from a third winding of the power transformer; and proximate the third winding. And a first feedback winding of the power transformer for generating a first feedback voltage representing a change in load on the power transformer; and a first feedback winding for the third winding. A second feedback winding of the power transformer, located farther from the winding, for generating a second feedback voltage indicative of a change in load on the power transformer; By controlling the switching of the output switching means An input circuit coupled to the first and second feedback windings for adjusting energy transfer between the energy source and the deflection circuit; and an output circuit coupled to the output switching means. A switching power supply having an improved regulation comprising a control circuit for more precisely regulating the energy supplied from the second winding to the deflection circuit, thereby stabilizing the dimensions of the raster.